The invention concerns a method of determining height of a series of jumps by double integration.
In rehabilitation therapy and the training of athletes, jumping force measurements are very important for performance diagnostics, for ascertaining the efficiency of the legs with regard to speed, coordination and endurance. For this both individual and multiple jumps are measured, the latter involving a series of jumps in immediate succession.
Measuring the vertical jumping force of the legs is accomplished with measuring platforms such as those covered by U.S. Pat. No. 5,913,242. Derived from this can then be a number of parameters like the jumping height and jumping performance. Fitted in the feet of such measuring platforms are force sensors which measure the jumping force continuously, transmitting within one second a large numberxe2x80x94typically several hundredxe2x80x94measured values to an evaluation facility such as computer. From this the measured results are plotted in the form of force curves for example.
From the shape of a measured curve the heights of a jump can be calculated by integrating twice. It is advantageous to define the time interval of a jump from standstill before the jump to renewed standstill after it. For determining the height of a single jump this method yields good results. With multiple jumps it fails, however, because the critical values of the starting conditions for the accelerations in the first integration and for the velocity in the second integration depend on the final conditions of the previous jump. With multiple jumps, small measuring and integration errors add up so seriously that the jump heights can no longer be calculated clearly and satisfactorily, leading to completely unusable results especially with longer series of jumps.
The object of the invention is to overcome this disadvantage when determining the heights of multiple jumps. It is achieved through the features in the present invention. With the invention, defined initial conditions are fixed for the acceleration and velocity for both integrations of each individual jump in a series of jumps. Through these starting conditions the small integration errors are eliminated in each case.
Advantageous refinements and enhanced precision of the new method take into account the special features of the first and last jump in a multiple jump series.
The time intervals selected for determining the standstill of a test person before the first and last jump may be typically 200 ms. Within these time intervals the following conditions must likewise be satisfied as xe2x80x9cpreset fluctuation rangesxe2x80x9d:
a) Within the selected time interval the average measuring signal must exceed 0.5 times the body weight, and
b) the standard deviation of the signal must not exceed 5% of the body weight within the selected time interval.
Condition a) ensures that the test person is really standing on the measuring platform, while condition b) ensures that he is standing relatively still. Of course other values and criteria may be taken for standing on the platform and for the xe2x80x9crestxe2x80x9d position.
Below the invention will be explained in more detail with reference to a typical embodiment and some drawings.
Other objects, advantages and novel features oft he present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.